When welding pipe sections to one another to form a pipeline it is conventional to apply a circular clamp to one of the pipe sections adjacent its free end and then use such clamp to position and support an end of a second pipe section in confronting relation to the one pipe section. The clamp conventionally is equipped with a plurality of axially extending jackbars of such length as to project beyond the free end of the pipe on which the clamp is mounted and provide support for the confronting end of the second pipe. Conventionally, the jackbars include radially adjustable jack screws which are operable to shift the second pipe radially of the first pipe to a position in which the confronting ends of the pipes are substantially coaxial.
The configurations of the ends of any two pipes rarely conform to one another. In most cases the pipe ends are oval, rather than circular, and the end of one pipe is more or less oval than the other. It is necessary, therefore, not only to support the pipes so that their confronting ends are substantially coaxial, but also to reform one or both of the pipe ends so that their configurations conform. It is customary to effect conformation of the confronting pipe ends by manipulation of the jack screws. Conventionally, the jack screws bear against only one of the pipes, as a consequence of which all of the reformation is applied to only one of the pipe members, thereby resulting in the imposition of considerable stress on the clamp.
Some of the clamping devices in use are composed of a pair of arcuate, rigid frame members which together form an annulus of such size as to encircle one or both pipes that are to be joined together. These kinds of clamps generally are capable of use with pipes whose diameters vary only slightly. Such clamps, however, may have radially adjustable jack screws that can be spaced at substantially uniform distances circumferentially of the clamp so as to apply reforming forces on one or both pipes and around the entire circumference thereof. Since such clamps are capable of use only with pipes of relatively uniform diameter, however, it is necessary for the pipefitter to have multiple clamps for use with pipes of different diameters.
A clamp of the kind that is adapted for use on pipes of greatly different diameters conventionally has a frame or block which seats on one pipe and to which is secured one end of a flexible chain. The chain encircles the pipe and passes through the frame so as to form with the latter a loop having an inside diameter corresponding substantially to that of the pipe. The chain is provided with jackbars which are adjustable circumferentially of the chain loop so as to provide circumferentially spaced supports for a second pipe, and the jackbars conventionally are equipped with radially adjustable jack screws capable of clamping and reforming the confronting end of the second pipe. Although the jackbars may be adjusted circumferentially of the loop formed by the chain and block, the frame itself normally is not equipped with any means for reforming either of the two pipes. As a consequence, those portions of the pipes underlying and adjacent the frame cannot be subjected to reforming forces. Thus, it is not always possible to conform the confronting ends of the two pipes to the extent desired.
In reforming the confronting ends of two pipes it sometimes is desirable to apply reforming forces to selected areas of one pipe and reforming forces to selected areas of the other pipe. However, most of the adjustable pipe clamps utilizing flexible chains or the like have jackbars which are not sufficiently adjustable axially of the pipes to enable reforming forces to be applied to either selected one of the two pipes. Further, those jackbars which are axially adjustable require loosening of the chains to effect such adjustments.
Pipe clamps of the kind utilizing flexible chains equipped with multiple jackbars conventionally require threading of the chain through all of the jack bars prior to mounting the clamp on the pipes that are to be welded together. As a result, the weight of the clamp may be substantial and more than can be handled conveniently by one person.
It is the object of the present invention to provide a pipe clamp which overcomes all of the objectionable characteristics referred to above.